Method for developing latent field images with liquid inks



July 2, 1963 R. M. SCHAFFERT METHOD FOR DEVELOPING LATENT FIELD IMAGES WITH LIQUID INKS Filed Dec 22 1958 2 Sheets-Sheet 1 VOLTAGE SOURCE FIG. I

SOURCE FIG. 4

FIG. 3

FIG. 7

////[// 22 I ISIS 21 INVENTOP ROLAND M. SCHAFFERT BY ATTORNEY ISISISI.

FIG. 2

July 2, 1963 R. M. SCHAFFERT 3,096,198

METHOD FOR DEVELOPING LATENT FIELD IMAGES WITH LIQUID INKS Filed Dec. 22, 1958 v2 sheets-sheet 2 VOLTAGE SOURCE VOLTAGE SOURCE llnited rates harem 3,tl%,l9$ METHOD FOR DEVELOEHNG LATENT HELD IMAGES WHTH LlQ'UlD HNKd Roland M. Schaifert, Vestal, N.Y., assignor to international Business Machines Qorpcration, New York,

N.Y., a corporation of New York Filed Dec. 22, 195%, tier. No. 737;,1itl7 4 flat-ms. (Cl. ll7-37) This invention relates to the art of printing and more particularly to nonmechanical printing where latent field images are to be rendered visible with liquid inks.

-In general, the art of nonmechanica-l printing involves the formation of latent images which manifest field properties, the development of a visual image from the latent image, and the utilization of the developed image for producing a more or less permanent reproduction. One well-known example of this type printing is commonly referred to as electrostatic printing according to which the latent image is formed of a pattern of electrostatic charge and development is obtained by the deposition of elect-roscopic pigmented particles on a surface of a carrier or print element bearing the image. Another type of nonmechanical printing is referred to as magnetic printing according to which the latent image is a magnetic flux pattern and development is obtained by the deposition of magnetically attractable particles over a surface bearing the image.

One of the principal difliculties associated with this type of printing is the formation of background. This is particularly true where it is desired to use liquid development material and where application of that material is to be made to a surface by impression.

Consequently, it is an object of this invention to provide an improved method for developing latent field images with liquid inks wherein application of said inks is by impression.

It is also an object of this invention to provide an improved method for developing latent electrostatic images with liquid inks by impression.

It is an additional object to provide an improved method for developing latent magnetic images with liquid inks by impression.

It is a further object of this invention to provide an improved method where printing with liquid inks and latent field images may be performed directly on a print medium. I

Briefly in practicing this invention, there is provided an impression member which is saturated with a liquid in'lc which is extractable from the impression member when contact is made with a surface on which development of the latent image is to take place. The extraction, as it is understood to exist in connection with this invention, may be attributable to forces exerted by the latent image acting upon charged particles of pigment or dyestuif suspended in liquid ink and'mechanical forces associated with and resulting from the contact, such as adhesion, absorption, etc. However, in accordance with this invention, the mechanical extraction forces are counterbalanced by the application of an electric field which opposes such extraction of the pigmented liquid by virtue of the contact. Thus extraction of the liquid ink and its deposition on the development surface will occur only in those areas where a latent image exists having a field of force effective to produce such an ex-. traction. Thus it will be appreciated that the inven tion provides a basis for printing with liquid inks by impression without'undesirable background. It can be further appreciated that the degree of mechanical extraction can be counteracted by adjusting the electric force. Consequently, the present invention affords the plate. prises a layer 15 which is a photoconductive insulator,

ing plates 22 and 24, respectively.

basis for printing directly on a liquid absorbent print medium or the like which overlays an image bearing member, such as an electrographic pr-int element. Other advantages will become apparent as the following description proceeds, while the novel features of the invention are set forth with particularity in the appended claims.

Other objects of the invention will be pointed out in the fol-lowing description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

FIG. 1 is an isometric view showing means for manually practicing one version of the subject invention.

FIG. 2 is a cross-section of a fragment of an impression member useful in practicing the subject invention.

FIG. 3 is a cross-section of a fragment of a further embodiment illustrating the construction of an impression member useful in practicing the subject invention.

FIG. 4 is a cross-sectional end view illustrating schematically the manner in which impression development is practiced in accordance with the present invention.

FIG. 5 is a schematic presentation of a continuous type of electrostatic printer apparatus incorporating the features of the subject invention.

PEG. 6 is a schematic presentation of a magnetic printer apparatus incorporating the features of the present invention.

FIG. 7 shows an alternate arrangement for supplying liquid inks to an impression member made in accordance with the present invention.

Referring to the drawings, FIG. 1 shows a print element ill bearing a latent electrostatic image 11, a sheet of a print medium 12 having a visual image 13 thereon, and a saturable impression member 14.

Print element ll? preferably takes the form of a plate member having a dielectric surface 15 superimposed upon a conductive substrate is and may preferably be of the type well known to those skilled in the art-as a x-erographic ln that form, print element It) therefore come.g., amorphous selenium, which is rendered selectively conductive upon exposure to a photoimage to selectively dissipate electrostatic charge formed over the surface thereof. Impression member 14 may take a variety of different forms but in one embodiment comprises a conductive porous plate 17, such as porous bronze produced by Well-known powder metallurgy techniques, which is capable of being saturated with a liquid ink absonbable by a print medium 12 or the like. For convenience in manual manipulation, impression member 14 may be provided with an insulating cover 18 to which is attached a handle Zti. A voltage source 24 preferably adjustable, is connected to plate 17 and substrate 16 for applying a potential thereacross.

Alternate embodiments of an impression member suitable for practicing the subject invention are shown in FIGS. 2 and 3. In FIG. 2 the impression member comprises a composite of an impression layer 21 formed of porous insulating material, such as porous rubber or plastic, attached to a conductive backing plate 22. Liquid retaining pores are figuratively represented by numeral 23. In FIG. 3 the backing plate takes the form of a conductive metallic screen 24- to which is attached an impression layer of porous insulating material 25 which may be felt or the like also having liquid retaining pores 23. In the embodiments of FIG. 2 and FIG. 3, of course a connection of the voltage source 26 would be to back- It is further understood that the embodiment of FIG. 2 may include a felt insulating layer, and the embodiment of FIG. 3 may include a porous rubber or any other suitable insulating :material.

would include any ink containing pigment or dyestulf particles dispersed in a suspended state in a liquid vehicle where the relation of the particle to the vehicle is such that a charge is produced on the particles, thereby making them and the liquid vehicle susceptible to control of the electric forces produced by the latent image and the control fields.

The specific inks selected for saturation of impression member 14 would depend upon whether latent image 11 is formed of negative or positive charge or whether a positive or negative image is to be reproduced. An example of an ink suitable for developing electrostatic images having a positive polarity might be as follows: A; to gram of Amaranth dye (Fisher Cat. No. A-7 89, .Colour Index 184) is added to 150 cc. of toluene. The dyestufi": is suspended in the toluene by mixing thoroughly in a Waring Blendor, after which the liquid dye mixture is strained through filter paper to obtain a finely-divided suspension of the dyestufi particles in the liquid. The dyestuff particles will be electrically charged to a negative polarity.

Where it is desired to develop images having a negative polarity, the ink may comprise /a to 4 gram of methyl violet 3B added to 150 cc. of hexane. The pro 'cedure for mixing is the same as in the preceding example.

This provides a suspension in which the dyestuff particles have positive electrical charges.

Further examples of suitable liquid inks may be understood by reference to an article appearing in the Journal of Scientific Instruments, May 1956, volume 33, pages 194 and 19-5.

Saturation of impression member 14 may be effected 'by dipping plate 17 into a vessel (not shown) containing a supply of suitable liquid ink previously mentioned or cover 18 may be of any well-known construction intended to retain a supply of such ink internally in contact with the reverse surface of layer 17. Where saturation is accomplished by dipping, it may be desirable to wipe the front surface of layer 17 with a doctor blade or the like to remove any excess ink adhering thereto. Subsequent to such saturation, the impression member 14 is then placed so that layer 17 is brought into contact with the upper surface of print medium 12. During the period of contact, a potential from voltage source 20 is applied to the impression member 14 which produces an electric field opposing and counterbalan-cing the mechanical forces tending to extract the ink from the porous recesses of impression member 14 by virtue of the contact between the surface of layer 17 land the upper surface of print medium 12. For a better understanding of this aspect of the invention, reference is made to FIG. 4 which illustrates the condition which prevails when impression member 14 is in contact with the print medium 12 and a potential has been applied by source 20 which counterbalances the extraction of ink from the pores 20 by the force attributed to the absorption by print medium 12. In those areas of print element layer 15 on which electrostatic charge exists, ink will be extracted from the adjacent liquid filled pores for deposition onto the upper surface of print medium 12 where it would become absorbed therein, thus forming a visual image 13. Following the impression contact, member 14 is removed, and

sheet 12 is removed from the surface of print element 12. The preceding steps may be repeated using the same or a difierent latent image. While FIG. 4 discloses the printing directly on a print medium 12, it is to be understood that the invention can be practiced where impression member 14 is brought to bear directly on the upper surface of print element 10. Printing directly on print medium 12 has the advantage of eliminating a transfer step and the need for cleaning the print element after development. Where development is effected on print element 10, it is expected that the mechanical forces of extraction from the contact between the print element 10 and impression member 14 would be due in good measure to adhesive forces, rather than absorptive forces. In this case the visual image on the surface of print element may be transferred to a print medium in any known manner, and the surface of print element wiped clean before use to print a second copy.

FIG. 5 shows the invention as it is practiced in connection with a printer apparatus adapted for printing on a continuous basis using electrostatic images. As shown in FIG. 5, the print element 10 is cylindrical in form and is supported by and in electrical contact with a conductive drum 26 which in turn is suitably supported in electrical contact by a suitably mounted shaft 27 which may be driven by any well-known motive device, such as an electric motor, not shown. Arranged sequentially in a radial manner about the surface of print element 10 are a corona discharge unit 23, a photoimage projection apparatus which may include lens 29, a liquid development apparatus including an impression member in the form of a porous roller 30, and an erasing optical unit 3 1. In accordance with this invention, impression roller 30 is a conductive porous member adapted to retain a supply of image extractable liquid ink 32 therein and in the present embodiment is preferably a cylindrical form of the impression member of FIG. 4 or FIG. 3. In the latter instance it would be expected that screen 24 would be sufliciently perforated to permit flow of ink therethrough to eifect the saturation of layer 25. A shaft 33 supports and is in electrical contact with roller 30 and is positioned so as to sustain roller 30 in contact with a print medium, such as web 34, which passes between roller 30 and the surface of print element 10 to have visible images 35 produced thereon. In passing through the development position, web 34 may be driven from a supply roll 36 between feed rollers 37 to a takeup reel 38. The driving connections for the takeup reel 38, the impression roller 30, and the drum 26 may be of any suitable type and might include a common motive source to which each of the driven elements is connected in a manner which will effect synchronous operation, if desired. A voltage source 20 for applying an electric field to the impression roller 30 has one side connected to shaft 33 and the other connected to ground. Shaft 27 is likewise connected to ground.

FIG. 6 illustrates a continuous type printer apparatus in which printing is produced from latent magnetic images which are rendered visible in accordance with principles of the subject invention. In this embodiment the print element is a magnetic drum 39 supported by a shaft 40 and having a permanently magnetizable surface on which magnetic flux images 41 can be produced by a suitable generator 42. As in FIG. 5, a print medium in the form of a web 34 has visible images 43 produced thereon as it passes in compression between roller 30 and drum 39 as it is moved from supply roll 36 over feed rolls 37 to a takeup reel 38. The impression member 30 in the embodiment of FIG. 6 is also preferably a porous cylindrical member saturable with an image extractable liquid ink 32, a supply of which is contained within the confines of the roller. In the embodiment of FIG. 6, impression roller 30 is a porous nonmagnetic material, and the liquid ink 32 is preferably an aqueous solution in which minute particles of magnetic material are dispersed.

would be as follows: A slurry of iron oxide is prepared by precipitation of Fe O from a solution of FeCl and FeCl with NaOI-I. A stabilizing solution is then made by adding two grams of cocoanut =oil amine (mostly dodecyl amine), as obtained from Armour & Co., to about cc. of normal hydrochloric acid to bring a pH of 7. The solution is then diluted with distilled water to 50 cc. and 20 cc. of the Fe O slurry added. After thorough mixing, the whole system is brought to 150 cc. with distilled water and stirred vigorously in a Waring Blendor. It is finally diluted again to a total of 600 cc. to provide the final product. The suspended magnetic particles are charged positively, and the polarity of the applied voltage would be selected accordingly.

Since in some applications it may occur that the extractive force of the magnetic image may produce some deposition of the liquid ink on the outer surface of impression member 30, it may be desirable to provide a wiping means, such as a doctor blade 44, for cleaning the surface at some point preceding engagement with the print medium. A similar means may be provided for the same purpose in the electrostatic printer embodiment shown in FIG. 5.

It has been found that dispersions of magnetic particles in an aqueous solution contain an electrostatic charge thereon. For that reason the absorptive extraction forces of print medium 34 can be counterbalanced successfully by the application of an electric field to the impression member 30 in FIG. 6. To accomplish such a result, voltage source 20 is connected to shaft 33 With which impression roller 30* is in electrical contact and to ground. Shaft 40 which supports drum 39 is also electrically connected to ground. An erasing means 45 may be provided at a radial position following the development station to effect the removal of magnetic images, if desired, prior to the next printing cycle.

In FIG. 7 the saturation of the cylindrical impression member 30 is effected by causing the outer surface thereof to be partially submerged in a supply of liquid ink 32 contained in an open vessel of any suitable type 46. In this case a porous member structure, such as shown in FIG. 2, may also be used. Any excess of liquid ink adhering to the outer surface of the impression member 30 will be removed by the wiping action of the blade 44 as the impression member 30 is caused to turn in a clockwise direction to be brought into engagement with the print medium (or the surface of the print element) as it moves through the development station.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to certain preferred embodiments, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, Without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

l. A method of developing latent field images compris- (a) contacting a liquid ink wet-table development surface of a latent image-bearing record medium in the image and non-image areas alike With an impression member having a developing surface uniformly saturated with an image attractable development surface wetting electrostatic field controllable liquid ink,

(b) and subjecting said liquid ink to an external electrostatic transfer control field while the developing surface is in contact with said record medium and said liquid ink is in contact coincidentally with the image and non-image areas alike of said record medium development surface by applying an external transfer control potential to said impression member and said record medium,

(c) said external electrostatic transfer control field having a polarity and magnitude opposing and counterbalancing the transfer of said pigmented liquid ink to the non-image areas while permitting transfer of said pigmented liquid ink from said impression member in response to field force of said field images in said image areas (d) whereby said pigmented liquid ink is deposited on said image areas and is prevented from depositing on the non-image areas of said development surface of said image bearing record medium on separation of said developing and development surfaces.

2. A method of developing latent electrostatic field images comprising (a) forming a latent electrostatic field image on an electrographic print element having a liquid ink wettable development surface,

(b) impregnating a liquid saturable impression member with an image attractable liquid ink comprising electrically charged pigment particles in a development surface wetting dielectric liquid medium,

(0) impressing the developing surface of said impregnated impression member on said development surface to thereby bring said pigmented liquid ink into contact coincidentally with non-image and image areas alike of said liquid wettable development surface,

(d) subjecting said liquid ink to an external electrostatic transfer control field while said impression member development surface and said print element development surface are in contact by applying an external control potential to said impression member and said print element,

(e) said control field having a magnitude and polarity opposing and counterbalancing the mechanical forces effecting transfer of said pigmented liquid ink from said impression member to said development surface of said print element while permitting transfer in the image areas thereof under field force attributable to said electrostatic images (f) whereby said pigmented ink in contact with the image areas is transferred from said impression member to said development surface and said pigmented ink in contact with the non-image areas of said development surface is retained on said impression member on separation of said developing and development surfaces.

3. A method of developing latent magnetic field images comprising '(a) forming a latent magnetic field image on a magnetizable print element having a liquid ink wettable development surface,

(12) impregnating a liquid saturable impression member with an image attractable liquid ink comprising electrically charged magnetizable pigment particles in a development surface Wetting liquid medium,

(c) impressing the developing surface of said impregnated impression member on said development surface to thereby bring said pigmented liquid ink into contact coincidentally with non-image and image areas alike of said liquid wet-table development surface,

(d) subjecting said liquid ink to an external electrostatic transfer control field While said impression member developing surface and said print element development surface are in contact by applying an external control potential to said impression member and said print element,

(e) said control field having a magnitude and polarity opposing and counterbalancing the mechanical forces effecting transfer of said pigmented liquid ink from said impression member to said development surface of said print element while permitting transfer in the image areas thereof under field force attributable to said electrostatic images (1) whereby said pigmented ink in contact with the image areas is transferred from said impression member to said development surface and said pigmented ink in contact with the non-image areas of said development surface is retained on said impression member on separation of said developing and development surfaces.

4. A method of preparing print copy comprising;

(a) forming a latent field image on an electrographic print element,

(b) superimposing a liquid ink absorbent print copy medium on said print element,

() impregnating an impression member with a pigmented image attractable liquid ink comprising electrically charged pigmented particles suspended in a print copy medium absorbable liquid vehicle,

(d) impressing said impression member on said superimposed print copy medium so as to apply said liquid ink to said print copy medium coincidentally to regions thereof superimposing image and nonimage areas of said print element,

(e) subjecting said liquid ink to an external electrostatic transfer control field While said ink saturated impression member and said print copy medium are in contact by applying an external control potential to said impression member and said print element,

(f) said control potential being applied with a mag nitude and polarity opposing and counterbalancing absorptive forces of said print copy medium on said pigmented liquid ink in said impression member While permitting absorption of said pigmented ink under field force of said image in the areas of said print copy overlaying the image areas of said print element i (g) whereby said pigmented liquid ink in contact with with the print copy overlaying said image areas is transferred from said impression member to said print copy and said pigmented ink in contact with the print copy overlaying said non-image areas of said print element is retained on said impression member on separation of said impression member and said print copy medium.

References Cited in the file of this patent UNITED STATES PATENTS 2,053,494 Pirie et a1 Sept. 8, 1936 2,319,615 Luehrs May 18, 1943 2,468,400 Huebner Apr. 26, 1949 2,551,582 Carlson May 8, 1951 2,752,833 Jacob July 3, 1956 2,763,204 Sims Sept. 18,1956 2,763,208 Rockoff et a1. Sept. 18, 1956 Y 2,811,465 Greig Oct. 29, 1957 2,877,133 Mayer Mar. 10, 1959 2,890,968 Giaimo June 16, 1959 2,892,709 Mayer June 30, 1959 2,899,335 Straughan Aug. 11, 1959 3,010,883 Johnson et a1. Nov. 28, 1961 FOREIGN PATENTS 755,486 Great Britain Aug. 22, 1956 215,754 Australia June 23, 1958 

1. A METHOD OF DEVELOPING LATENT FIELD IMAGES COMPRISING (A) CONTACTING A LIQUID INK WETTABLE DEVELOPMENT SURFACE OF A LATENT IMAGE-BEARING RECORD MEDIUM IN THE IMAGE AND NON-IMAGE AREAS ALIKE WITH AN IMPRESSION MEMBER HAVING A DEVELOPING SURFACE UNIFORMLY SATURATED WITH AN IMAGE ATTRACTABLE DEVELOPMENT SURFACE WETTING ELECTROSTATIC FIELD CONTROLLABLE LIQUID INK, (B) AND SUBJECTING SAID LIQUID INK TO AN EXTERNAL ELECTROSTATIC TRANSFER CONTROL FIELD WHILE THE DEVELOPING SURFACE IS IN CONTACT WITH SAID RECORD MEDIUM AND SAID LIQUID INK IS IN CONTACT COINCIDENTALLY WITH THE IMAGE AND NON-IMAGE AREAS ALIKE OF SAID RECORD MEDIUM DEVELOPMENT SURFACE BY APPLYING AN EXTERNAL TRANSFER CONTROL POTENTIAL TO SAID IMPRESSION MEMBER AND SAID RECORD MEDIUM. (C) SAID EXTERNAL ELECTROSTATIC TRANSFER CONTROL FIELD HAVING A POLARITY AND MAGNITUDE OPPOSING AND COUNTERBALANCING THE TRANSFER OF SAID PIGMENTED LIQUID INK TO THE NON-IMAGE AREAS WHILE PERMITTING TRANSFER OF SAID PIGMENTED LIQUID INK FROM SAID IMPRESSION MEMBER IN RESPONSE TO FIELD FORCE OF SAID FIELD IMAGES IN SAID IMAGE AREAS (D) WHEREBY SAID PIGMENTED LIQUID INK IS DEPOSITED ON SAID IMAGE AREAS AND IS PREVENTED FROM DEPOSITING ON THE NON-IMAGE AREAS OF SAID DEVELOPMENT SURFACE OF SAID IMAGE BEARING RECORD MEDIUM ON SEPARATION OF SAID DEVELOPING AND DEVELOPMENT SURFACES. 